Enlarge / This aerial picture taken on December 8, 2023, shows the US-Mexico border wall in Sasabe, Arizona. (credit: VALERIE MACON/AFP via Getty Images) In a vast stretch of the Sonoran Desert, between the towns of San Luis Río Colorado and Sonoyta in northern Mexico, sits a modest building of cement, galvanized sheet metal, and wood—the only stop along 125 miles of inhospitable landscape dominated by thorny ocotillo shrubs and towering saguaro cactuses up to 50 feet high.